londiste.drop_obsolete_partitions: reformatted
londiste.create_partition: properly quote owner in ddl
londiste.drop_obsolete_partitions: changed back to return (and log) names of dropped tables
londiste: moved drop_obsolete_partitions() call to check_part()

Note that current behaviour is that dispatcher would crash if events older than retention period arrived.
Perhaps it is better than quietly recreating and redropping tables for too old events..?
londiste: sweeping change to postpone log string formatting